This invention relates to waste water treatment systems, and more particularly, to such systems wherein provision is made for the oxidation of organic matter contained in the waste water while the same is being moved in a closed path.
Many waste water treatment facilities in use today are of the so called "activated sludge" type. Typically, such systems are provided with an oxidation or aeration basin or vessel in which the waste water follows a flow path that is a closed loop. In the usual case, raw waste water containing organic solids is introduced into the flow path after prior treatment to remove grit to prevent such grit from entering the oxidation vessel and accumulating therein. The input stream mixes with the recirculating stream, that is, the mixed liquor, and an oxygen containing medium, usually air, is introduced into the vessel to oxidize the organic material. Part of the mixed liquor is withdrawn and typically routed to a settling basin.
Typically, the grit chamber used constitutes a separate vessel upstream of the oxidation vessel wherein grit is removed. Grit is normally considered to be small inorganic particles such as sand or cinders which have a size about 200 U.S. mesh. To remove such grit, prior art grit chambers utilized raw or partially treated waste water as a fluid medium to effect liquid scour and allow centrifugal separation. To provide liquid velocity necessary to effect separation, mechanical devices such as pumps, impellers, air diffusers, or the like are required. Alternately, the necessary liquid velocity was provided by that of the incoming waste water which frequently would be mechanically advanced by a pump remote from the treatment facility.